I'm not expert, but let's take a crack! :)
She has an overly long, thinish neck and a huge head. She's post legged in the back and possibly cow hocked. Her pasterns are thin and weak looking. Her cannon bones are also pretty thin. Generally, she looks very... Off balanced. Disproportionate.
She just looks like she doesn't have enough bone to support her body weight. I would not use a horse with legs that off for jumping.